Remote-control system, particularly for arc welding



In Uentor hglfvrr l Attorneys m u 7, m m ,mw R zm k uw M, La m n R m W/Nm om mm Nm mm s Fw TQQ m QM. m www NQ Hu U NS Q im U9 NOW 9m m 9 M w RQQ 8, m u d NW m F Nov. 8, 1949 F. RIMMINGTON 2,487,375

REMOTE-CONTROL SYSTEM, PARTICULARLY FOR ARC WELDING' Filed June zo, 1945e sheets-sheet 2 A C. 93C mms.

Inventor ymw, uhmm ai@ Nov. 8, 1949 fP/leg, June 20, 1945 F. RIMMINGTONREMOTE-CONTROL SYSTEM, PARTICULARLY FOR ARC WELDING 6 Sheets-Sheet 5 Arra/eur:

Nov. 8, 1949 RIMMINGTON 2,437,375

REMOTE-CONTROL SYSTEM, PARTICULARLY FOR ARC WELDING- Filed June 20, 19456 Sheets-Sheet 4 Ac ,I F0025 @E '5%,MMJM

A TTOR/YEYJ Nov. 8, 1949 F. RIMMINGTON REMOTE-CONTROL SYSTEM,PARTICULARLY FOR ARC WELDING A 6 Sheets-sheet 5 Filed June 20, 1945 220K4%Cl Inventor Nov. 8, 1949 F, RnMMlNGToN 43.32375 REMOTE-CONTROL SYSTEMLPARTICULARLY FOR ARC WELDING Filed June 2o, 1945 6 sheets-sheet e `Hllllll Mmmm! TFA/N A Attorneys Patented Nov. 8, 1949 OFFICE lREMOTE-CONTROL SYSTEM, PARTICU- LARLY FOR ARC WELDING Frank Rimmington,Potters Bar, England Application June 20, 1945, Serial No. 600,511 InGreat Britain June 12, 1944 2 Claims. l

The present invention relates to the remote control of electricgenerators or other current supply means, whereby the output of thegenerator or other current supply means may be varied or adjusted from aremote point. The invention is particularly applicable to the remotecontrol of generators or transformers for arc welding.

In the specification of my copending application Serial No. 506,746, nowPatent No. 2,443,776, a remote control system is described in which thecontrolling circuit is shunted across the arc, the voltage variationacross the arc with different positions of the electrodes being used tocontrol the operation of voltage selective relays whereby on shorteningthe arc, for example by scribbling the electrode on the work, the outputcurrent controller may be adjusted in one direction whilst, bylengthening the arc, the controller may be adjusted in the oppositedirection.

In practice, it has been found that with some generators andtransformers it is not easy to reduce the voltage across the arc to asufficiently constant value to ensure operation of the correspondingvoltage selective relay by scribbling the electrode, if this is longerthan about four inches. Although this difficulty has been overcome byinstructing the operator to change his long electrode for a stub orscrap Whenever he wished to reduce the current, this involves a waste oftime.

An object of the present invention is to provide modifications of thearrangement described in my aforementioned specification which enablesthe above disadvantages to be overcome.

In one form, the invention consists in a remote control arrangement inwhich the drawing out or shortening of the arc prepares a circuit forthe motor of the output current controller, the circuit being completedto drive the motor in either one direction or the other depending uponthe time interval during which the arc is drawn out or shortened beforebeing returned to its normal welding position. Thus, for eX- ample, ifthe arc is drawn out and immediately, say within five seconds, returnedto the normal welding position, the output current controller will bedriven in one direction, whilst if the arc is drawn out for a longertime, say for longer than ve seconds, then the output current controllerwill be driven in the opposite direction. When the motor has beenstarted by drawing 4and holding the long arc, the arc may be re-v storedto its normal welding dimensions, so that for both directions ofoperation of the output current controller the electrode may be held inits normal welding position with the normal weldlll ing arc whilst theadjustment is taking place whereby the operator can see .by the colourand behavior of the arc when the current has reached the desired value.The operating action in either case may be arrested by simply breakingthe arc and re-striking it.

Fig. 1 of theaccompanying drawings shows a remote control arrangement inwhich the current may be reduced by drawing a long arc for a moment andthen immediately returning the electrode to the normal welding position,and in which the current may be raised by drawing a long arc and holdingit for-a longer time before returning it to the normal welding position.Since for both reducing and raising the current a long arc is drawn7 thediflicultes experienced with the previous arrangement in obtaining thecorrect voltage for reducing the current by scribbling the electrode onthe work are eliminated.

In Fig. 1, those relays whose function is the same or similar to therelaysshown in the drawings of my aforementioned copending applicationSerial No. 506,746 are similarly numbered. Thus, the relays RI and R3control the current down and current up" directions of rotation of themotor respectively. Relay R2 controls both directions whereas in theprevious arrangements it only controlled the down direction. lR4 is theopen circuit relay whose function is to neutralise the Whole apparatusunder this condition. In the present arrangement, however, it -is alsoused to stop the motor when the current has reached the desired values.

Relay RSI is an additional relay which co-ntrols the circuits of relaysR3 and Rl. Relay R3! is provided with a slow releasing coil to preventits armature from falling off during the brief breaks when the ContactR3?) operates. Alternatively, the RSD contacts may be of themake-before-break type in which case relay R3I need not be slowreleasing.

The voltage values shown at the top and bottom right-hand corners of therelay coil denote the voltages at which the relays operate and releaserespectively.

The relay R2 is shunted by a condenser C and .a resistance P so thatthis relay has a time delay action, the value of which may be adjustedby the condenser and resistance circuit. Za and Zb are two adjustableresistances for controlling the voltage at which the relay R3Ir-eenergises and releases and the adjustable resistance Zc is likewiseprovided for adjusting the voltage at which the relay R4 energises. Allthe relays 'are shunted across the arc circuit as shown and operate asfollows.

It will be assumed that the operator is welding and desires to reducethe current output from the generator or other current supply means. Todo this he draws a long arc of approximately one inch `which increasesthe arc voltage to 37 volts, whereby relay'R3l is operated and actuatesits contact R3Ia to complete the Lcircuit ofthe relay R3 and break thecircuit of the relay R2.

Since the condenser C has been charged .it holds'. Relay R3 operates and.byclosng its` relay R2. contact R3c it prepares a circuit `to.relay Rl.Relay RI .cannot operate, however, because it is short-circuited throughthe contacts `R31: and At its contact R31), the relay R3 changes.,

R3la. over the resistance in series with relay 1R31 v.to prepare thereleasing circuit for this relay through the left contact of R317. Aspreviously mentioned, the relay R3! is slowreleasingr or the contactsR31) -are of the -fmake-before-breakv type so that the relayRldoesfnot'fall oi during this change over. At its contact `R311 the relayR3 .prepares a circuit for `the-clockwise rotation of the motor M,vwhich is an A. C;/ D. C. series motonbut the motor does not operateowing to the left-hand contacts of RZa and R227 being open. l

The operator thenimmediately returns the arc towelding lengthwhereupontthe'arc voltage drops to approximately -25'volts and relay R31releases through the left-hand contact of R312. The circuit of the relayR2 is re-made by the contact R3laclosing its bottom contact and thistakes place before the condenser has had `time to `discharge and releasethe relay R2, Although the movement of contact Slappens thecircuit :ofrelay R3 through its up-per contact, the .relay :R3 does not falloiflcuty is heldithrough itsR3c contact and relay R1. This energizesrelay -RI which at its contact Rla closes .the motor circuit to drivethe motor in theanti-clockwise direction to 'drive the output currentcontroller in a directionto reduce the current.

When the operator sees by the colour land behaviourof the arc that -thearc current has reached the desiredrvalue, he arrests the movement ofthe output-current controller by fbreaking the arc. The arc voltage.thus rises to the open circuit value'andrelay yRl -operates to breakthe common return-of all-the other relays at its contact Rlla. Relays R3and RI release.and,in turn, release their contacts, R3breturning to theright-hand contact and the -motor circuit 'beiner broken at Rl'atostop-the motor.

The operator lthen re-strikes the arc-whereupon the arc voltage fallsto4 approximately zero, thereby releasing relay R4 whichcompletes at itscontact Rita the common return to all the other relays. `Allthe 'relaysremain de-.energized due to zero volts across the arc. The shortcircuitcaused by striking vthe faro also discharges the condenser v.C to.release relay R2 which changes its contacts R2a andRZb to theirlefthan-d positions. At lits contact R20, it Icloses Ia short-circuitacross the resistances Zq, =andZb, but .relay R3I is not, effected id-uetothe zero voltage across the line and the motor is not operated. Ondrawing ,the arc to its normal welding length, the voltage across the'arc `rises approximately to 25 volts. about -10 volts and restoresitscontacts R2a and R217 to their right-hand positions, vbut the motordoes not operate Vdue to the contacts R311l and Rla being open.. ContactR20 opens the short-circuit across the resistance-Zay and `-Zbf- Theyoperator The relay R2 energises at can then continue welding at there-adjusted values.

To move the output current controller to increase the arc current, theoperator draws :a long arc and holds it for a longer time so as to allowthe condenser C .to discharge and allow relay R2 to fall off. The time'period may, for example, befive seconds, On drawing the long arc thearc voltage rises to 37 volts-and relay R3| operates as previouslydescribed to complete the circuit 4of relay R3 and break the circuit ofrelay R2 at its contactR3l a., VAs previously, relay R3 oper- `ates and`prepares a circuit for the relay Rl at its contact R30, but the relay Rlcannot operate dueto the short-circuit through contact R30 and R3la.Contact R317 changes to its left-hand position and prepares thereleasing circuit 0f relay RSI. `Contact R3a closes and prepares acircuit for the clockwise rotation of the motor M.

After a time delay of say ve seconds, the relay R2 :releases ,owing-tothe e discharge of: -itsf-1con densery C.; Thereuponcits :contactsvRZa-.and 3R21; `change to. their Vleft-handypositionseandcsoscornpletefthe motor circuit 4,throughrthecontactfRSa, 4whereby .the ,motor isdriven in-the clock-wise direction anddrives theA outputwcurrentx con:-trollerltoin-crease theicurrent. yAt Aits :contact R2c relayRZshOrt-circ-uits theresistances Za and "2b.

As soon as the operator -fsees -in :the longs-arc that the current risrising, Vhefknows that the. time delay period hasmpassedizand y'that:hefcanxreturn his electrode to its normal, welding position. -Hjaving:done this:, he can observe vthe .risingrcurrent, at thefcorrect iarclength. Whenthe arc :is returned V-to, its normal length; the :relayR13] remains energised ,although the-arc voltage has nowdropped belowthe releasing value .of 30 volts with theresistance .ZIJ` infseries,`-since this resistance is Isl-iort-circuited@by thecontact R20.l/'henyth'el :arc current -has reached the :desired setting the arc isvbroken as previously :described torarrest the movement of. thecurrentacontroll'er. In thiscase the relay R2 remains releasedwithits-.contacts R2aandR2b intheir left-.handipositions, .and R20 vstillshort-circuits the. resistances Za: .andfZorfbut relayR'3ireleaseshecausefzthe common return is broken .at '.R'lla. They arcfisthen re-struck as previously described,'the relay Rfi remainingreleasedfdue tozerofvolts'across tlieyarc.A Upon drawing the arctofiits:normal welding length, however., the relay R2 makes as the-arc 4voltagereaches-ild'volts, Vthus breaking the short-circuit acrossftheresistancewinrseries with relay .and preventing :relay .R31 lfromenergising untilthe `operator has occasion tofalter the :current `valveby` again drawing :along arc.

Fig. 2 shows a modiiedand simplified arrangement as in thearrangementdescribed in Fig. "1, scribbling for the purposefof adjustingvthe-currentis dispensed within the apparatus according to .thisLmodification., .the current being adjusted inyone; direction by drawingout the arcand either holding it` draw-nout or restoring it to :itsvnormal Welding-position, and inthe oppositeifdirec'ti'on by.:making adeadfshort` by pressingth'e-electrodenor-the electrode holder onto thework and maintaining the dead short duringfthetime -of adjustment. l

In the prefer-red form `of this arrangement,

adjustment oithefcurrent in one-'direction 'is effected vbyv drawing-.along'arc-and y'holding-it until `the desired adjustment-hasibeenmadeiand adjustment in the opposite" directionfis eiected by-.mak-ing :a deadshort and'holdi--ng'iti sohlo'ng as the adjustment is being made.Preferably, the current is reduced when the electrode is pressed againstthe work to create a dead short so that the operator can easily memorisethe operation of the apparatus as follows.

Current down-electrode down and hold down. Current up-electrode up andhold up.

Thus, in the preferred form of the arrangement, to reduce the currentthe operator makes a dead short by pressing the electrode, or theelectrode holder, on to the work whereupon, after a slight delay, thecontrol motor starts and continues to turn the output current controllerto reduce the current so long as the short circuit is maintained. Tostop the motor the arc is struck. To raise the current the operatordraws and maintains a long arc. Again, the motor starts aftera slightdelay, but in the opposite direction,

and continues for so long as the long arc is held, the operatorobserving from the arc when the current has reached the desired value.To stop the motor the electrode is returned to its normal weldingposition. The apparatus, therefore, provides visual control of therising current only, but this is no serious drawback since visualcontrol during reduction of the current has been found to beunnecessary.

In Fig. 2 those relays of which function is the same or similar to therelays shown in Fig. 1 are similarly numbered. Thus, the relays Rl andR3 control the current down and current up directions of rotation of themotor respectively. Relay R2 controls both directions and relay R4 isthe open circuit relay.

The voltage values shown at the top and bottom right-hand corners of therelay coils denote the voltages at which the relays operate and releasev respectively.

The relay R2 is shunted by a condenser C so that this relay has a timedelay action. SI and S2 are two adjustable resistances for controllingthe voltages at which the relays R3 and R4 energise, and the resistanceS2 is a protective resistance in series with the relay R2 and condenserC. All the relays are shunted across the arc circuit as shown, thedrawing showing the condition of the circuit during normal welding.

- In the supply circuit of the motor M, which is an A. C./D. C. seriesmotor, are three sets of switch contacts R3a,. R31) and R2a. ContactsR3a and R3b are actuated by the relay R3 and are in eifect reversingcontactsy normally resting in the right-hand position shown but movingover to the left-hand position when relay R3 is energised. Thus, therelay R3 merely prepares the motor circuit for the required direction ofrotation before the time delay relay R2 releases to close its contactsR2a to complete the motor circuit.

The circuit of the time delay relay R2 can be broken at two points,namely at R3a when the arc voltage is increased to 33 volts by drawingand holding a long arc when relay R3 energises to open its contacts R3c,and at Rl a during a dead short when the relay RI is de-energised andopensgits contact Ria.

During welding only relays RI and R2 are energised. On open circuitrelay R4 only breaks the current of relay R3 so that during open circuitthe three relays RI, R2 and R4 are energised.

The mode of operation of the circuit is as follows. lIt will be assumedthat the operator is welding and desires to reduce the current outputfrom the generator or other current supply means. To do this he makes adead short by pressing the electrode, or the electrode holder. on to thework which reduces the arc voltage to between approximately 2 and 8volts depending upon the length of the cable. This de-energises relay RIwhich is designed to release at 10 volts, thus opening the circuit ofthe time delay lrelay R2 at its contact Ria. The relay R2, however, doesnot release for a short time due to the condenser C, and a convenientholding time for the relay R2 has been found to be 11/2 seconds. Afterthe condenser C has discharged the relay R2 releases and at its contactR2a completes the motor circuit via the contacts R3a, R3b in theirrighthand positions (since R3 is still deenergised) to start the motor Mrunning in the direction to reduce the output from the output currentcontroller. The motor M will continue to run in this direction until thecontroller reaches the minimum position when it opens the limit switchB, unless the dead short has previously been broken, which action alsostops the motor. In the latter case a temporary open circuit is createdand the arc voltage rises to a minimum of 45 volts which energises relayR4 and also breaks the circuit of relay R3 at Contact R4a. Thus, therelay R3 still remains deenergised and does not change over its contactsR3a and R31).l

Meanwhile relay RI energises to complete the circuit of R2 through theshort circuit contacts R2b across the protective resistance S2.

The re-striking of the arc produces only a fleeting short circuit sothat although relay RI releases and breaks the circuit of relay R2 atRia, relay R2 is held by the condenser C and the motor is not started.On drawing the are to its normal length the arc voltage increases toanything between 15 and 30 volts with peaks of 40 volts. These fleetingpeaks cause relay R3 to oscillate and break (at 33 volts) and make (at26 Volts) the circuit of relay R2 at contact R3a, but the motor is notaffected because again the condenser C holds the relay R2 energised andhence the contacts R2c remain open. When the arc voltage settles down toapproximately 2O volts relay R3 ceases to oscillate and remainsde-energised.

In order to increase the current output the operator draws a long arcand holds it. The arc voltage then exceeds 33 volts which energisesrelay R3. This breaks the circuit of the relay R2 at contact R30 andafter a time lapse of 1% seconds during which the condenser Cdischarges, the relay R2 releases to complete the motor circuit at R2a.In the meantime, however, relay R3 has shifted its contacts R3a and R317to their left-hand positions so that upon contact R2a closing the motorM is started but in the opposite direction so as to move the outputcurrent controller in a direction to raise the current output. Thecurrent will continue to rise so long as the long arc is held or untilthe output current controller reaches its maximum position and opens itslimit contacts A. When the operator observes from the arc that thecurrent has reached the desired value he returns the arc to its normalwelding length which reduces the arc voltage to below 26 volts therebyreleasing the relay R3 which closes its contacts R3c to complete thecircuit of the relay R2. Relay R2 opens its contacts R2a to stop themotor, and contacts R3a and R3b return to their normal right-handpositions. The operator then proceeds with his work with the currentheld at the new value.

A further modication of the invention consists in controlling theadjustment of the current the same manner, for example, upon the numberof times the arc is drawn out or shortened or short circuited. In oneembodiment, to reduce the current the arc may be short circuited onceand to raise the current it is short circuited twice. According to afeature of the invention, to adjust the current in one direction thenormal arc is altered to another condition for a predetermined minimumtime and to alter the current in the opposite direction the normal arcis altered to another condition for a predetermined minimum or maximumtime, is restored to its normal or another condition, and then returnedto the first changed condition for another predetermined time. Whilstthe voutput current controller is moving in one direction or the other,the arc may either be maintained in its changed condition as long as thearc current is being changed or it may be restored to the normal weldingposition so that a visual indication is obtained of the changing arccurrent.

In the preferred form of this modiiication, the current is adjusted inthe downwards direction by producing a dead short by pressing theelectrode or the electrode holder on to the work and maintaining thedead short for a predetermined minimum time, say of two secondsduration. To raise the current a fleeting dead short is producedfollowed by a longer dead short of the predetermined time duration ofsay two seconds. In one embodiment, the output current control motorwill start in the appropriate direction at the end of either of the twosecond periods, and will continue to alter the current value so long asthe dead short is maintained beyond the two second period, the motorbeing stopped by removing the dead short when the operator considersthat the arc current has reached the required new value.

The operator then restrikes the arc and proceeds with the welding at thenew current value. In an alternative embodiment the arc has to berestruck after the dead short operations in order to start the motor,whereby the falling or rising current will be visible in the arc. Inthis case the motor may be stopped by open-circuiting the arc for apredetermined time interval, after which the arc may be restruck and thef welding proceed at the new current value.

Figure 3 shows the circuit of a remote control arrangement in which thedirection of adjustment is controlled by the number of times the arc isshort-circuited, the adjustment continuing so long as the short-circuitis maintained.

Figure 4 shows a modification in which the arc is restored to its normalvalue for visual control during the adjustment. Referring to the circuitshown in Figure 3, the apparatus comprises six relays RI to R6 which aresufxed to indicate the number of relay contacts controlled by eachrelay. Only one of thesevrelays, namely, Rl is shunted across the arccircuit, the remaining ve relays being operated from a separate -voltsupply. Relay R2 is shunted by a condenser CI so as to give it a timedelay release operation of approximately one second; relay R6 issimilarly shunted by a condenser C2 giving a time delay release ofapproximately 11/2 seconds. M represents an A. C./D. C. series motorcontrolling the output current and A and B the limits which open themotor circuit in the positions of maximum and minimum current output.Contacts 3a, and

3b are actuated by the relay 3 and constitute reversing contacts for themotor circuit, normally resting in their left hand position, as shown,

for clockwise rotation of the motor to raise the arc current but movingover to their right hand positions when the relay 3 is energised todrive the motor in the anti-clockwise direction to re,- duce the arccurrent.

The circuit shows the relays in their conditions during normal welding.The mode of operation of the circuit is as follows. It will be assumedthat the operator is welding and desires to reduce the current outputfrom the generator or other current supply means. To do this he makes adead short by pressing the elec-l trode, or the electrode holder, on tothe work which de-energises the relay RI. At its contacts Rla a circuitis completed to energise the relay R2 and at its contact Rlb it closesone of the switches in the motor circuit but the motor cannot operatebecause contact RBa is open.

Relay R2 energises and at its contact R2a completes the common return ofall the relays R3, R4 and R5. Only relay R3 operates, however, throughthe left hand contact of R4b and contact Ria. At its contact R30 therelay R3 pre# pares a circuit for the relay R4 but this relay cannotoperate as the winding of R4 is shunted by the contacts R4b and Rl'a.The relay R3 also shifts its contacts R3a and R32; to their right handpositions to prepare the circuit of the motor anti-clockwise rotation tomove the -current controller in a direction to reduce the fcur` rentoutput. At its contact R3d it also opens the circuit for the relay R6.

After a time delay of ll/z'seconds, the condenser C2 has discharged andrelay R6 releases to complete the motor circuit at its contact Rla,whereupon the motor starts and the arc current is reduced.

The operator holds the short circuit until he considers that the currenthas reached the re-V quired new value and stops the motor byopencircuiting the arc. This energises relay Rl which breaks the motorcircuit at contact Rib and at its contact Rla it breaks the circuit forthe re-f lays R2 and R3. Relay R2 remains energised, however, for ashort time due to the time delay condenser CI shunted thereacross, sothat the common return lead to relays R4 and R5 through the contact R2ais not broken. Since the short circuit across the winding of the relayR4 has been removed by the opening of contact Ria, re-

lay R4 energises and closes a locking circuit for' itself at contactR4a. This short-circuits the relay R3 which releases and its contactsR3a and R311 return to their left hand positions and contact R3d againcloses the circuit of the relay RG. Relay R4 changes its contact R41)over to its right hand position to prepare a circuit for the relay R5through contacts R2b and R2a. However, after one second the relay R2releasesl due to the discharge of its condenser and breaks the commonreturn at its contact R211. Relay R4 thus releases and contact R413returns to its left hand position and cancels the prepared cir-^ cuitfor relay R5 which is now broken at two other points, namely, contactsR2a and R2b.

Restriking the arc produces iieeting dead shorts, possibly three or fourin rapid succession.'

The iirst fleeting impulse energizes relay R3 butall succeeding impulsesare transferred to relay R5 through the right hand contact of R413 sincerelay R4 has been energized when the circuit of relay R3 was broken atthe end of the ilrst im.

pulse, over the circuit previously described. The

second the condenser CI discharges and relay R2 releases to break thecircuit of relays R4 and R at contacts R2a and R21). Contact R5a remainsclosed thus maintaining relay R6 energized which keeps its contact RSain the motor circuit open. Relay RI, when it is energised, also opensthe motor circuit at its contact Rlb.

To increase the current a fleeting "dead short is produced followed by afleeting open-circuit and then a continuous dead short. The fleeting"dead short de-energises the relay RI which operates relays R2 and R3and prepares the circuit for relay R4 as previously explained. Onopening the dead short the relay RI again energises and at its contactRl a breaks the circuit of the relays R2 and R3. Relay R2 holds itscon-v tacts R2a and RZ'b closed so that relay R4 is energised and movesits contacts R41) to its right hand position to prepare the circuit forrelay R5. Contacts R3a and R3?) return to their left hand positions onrelay R3 being de-energised. After the fleeting open-circuit acontinuous dead short is produced. This again energises relay RI whichcloses its contact Rla to complete the circuit of the relay R5 throughthe right hand contact of R41) and contacts R2b and R2a. At

its contact Rlb,'the relay Rl also closes one of the. switches in themotor circuit. The relay R5 is thus energised and opens its contact R5ato break the circuit of the relay R6. After a delay of 11/2 seconds thecondenser C2 discharges and relay RE releases to complete the motorcircuit at its contact Ra. The motor thus starts to move in a clockwisedirection to drive the current controller in a direction to raise thecurrent, the operator holding the dead short until he considers that thecurrent has reached the requiredk The motor is then stopped byopen-circuiting the arc. This energises the relay RI to break thecircuits of relays R2, R4 and R5 at its contact Ria, and at its contactRlb opens the motor circuit to stopthe motor. Relay R5 releases andcloses the circuit of the relay R6 at its contact R5a. Relay R6 thusalso breaks the motor circuit by opening its contact Ra. After a periodof one second, condenser CI discharges and relay R2 releases to breakthe common return at its contact R2a. Relay R4 then releases and itscontact R4b returns to its left hand position ready for the nextoperating impulse. The arc is then restruck as above described and thewelding proceeds with the current held at its new setting.

If a series of short impulses are transmitted by tapping the electrodeholder on the work, these impulses Will, with the exception of the rstimpulse, cause contact R5a to oscillate, but the motor will not bestarted due to the relay R6 being held by its condenser C2. If theelectrode holder is left lying o-n the work, this is equivalent to onelong impulse which after the predetermined time delay starts the motormoving in the anticlockwise direction so reducing the current to aminimum. The motor stops when the limit switch B is reached and thecontinuous dead 10 short through the generator is reduced to a minimuanthus giving automatic protection to the generator.

Figure 4 shows a modified circuit arrangement in which, to reduce thecurrent a dead short is produced for 11/2 seconds and then the arc isstruck. This starts the motor and the falling current can be seen in thearc. The motor is stopped by open-circuiting the arc for one second andthen restriking the arc when welding can proceed with the current heldat its reduced value. The current is raised by first tapping theelectrode holder on the work once in order to produce a fleeting deadshort followed by a dead short of 11/2 seconds duration, the arc thenagain being restruck. This time the current will be seen to increase andcan be held at any desired value by again breaking the arc for onesecond. The arc is then restruck when the current will be held at thenew value.

The circuit is Very similar to that illustrated in Figure 1 except thatan additional relay Rl' is shunted across the arc circuit which has twocontacts Rla and Rlb, one in series with the relay R2 and another in themotor circuit. Relay Rl lonly energises upon open circuit of the arc sothat its contacts are normally closed. Relay RG is also provided with asecond contact RS?) in parallel with contact Ria.

To reduce the current the operator produces a dead short across the arcfor 1% seconds which releases relay RI. Contact Ria energises relay R2through the left hand contact R4b and contact R'la. At its contact Ribthe motor circuit is broken at a second point, it being also open atcontact Ra. Relay R2 closes its contact R2a to complete the commonreturn circuit of relays R3, R4, and R5, and relay R3 energises overcontact R417 in its left hand position. Relay R3 closes its contact R30to prepare the circuit for relay R4 but, as previously, relay R4 doesnot energise as it is short-circuited by the contact Ria. Relay R3 alsomoves its contacts R311 and R31) to their right hand positions toprepare the motor circuit for anticlockwise rotation to reduce thecurrent output. Contact R3d opens and after a delay of 11/2 secondsduring which condenser C2 discharges, relay R6 cle-energises and closesits contact REa. It also closes its contacts Rlb to lock the relays R2and R3.

On restriking the arc Contact Rl oscillates but relays R2 and R3 remainheld over over the locking contact RBb. Drawing the arc raises the arcvolts to over 15 volts. This energises relay Rl and its contact Riaceases to oscillate and remains open but relays R2 and R3 still remainheld over contacts R619 which now shunts the relay R4 to prevent it fromenergising. Contact Rlb closes to complete the motor circuit which thencommences to rotate ina direction to reduce the output current. Thefalling current can be observed in the arc.

The motor is stopped by open-circuiting the arc, for one second orlonger. This causes relay Rl to energise which opens its contacts R'lbto stop the motor and also its contacts R'la to break the circuit ofrelay R2. The condenser Ci discharges and after one second the relay R2deenergises and breaks the common return circuit of relays R3, R4 and R5at its contact R20.. Contact R3d is therefore closed to energise relayvR6 which opens its contact RSa to break the motor circuit and itscontact R6b to break the locking circuit of the relays R2 and R3. RelayR3 also opens its contact R30 to break the prepared cir- "tion andcontacts RZb and RZa.

cuit of "relay'fR4wand its contacts'RSaand R3b return to their vlefthand positions.

On restriking the arc relay Rl is deenergised and contacts Ria andRlboscillate, but the mo- -tor cannot start because its circuit is alsobroken rat contact Riia. v

The first make of contact Rla sends a fleeting ,impulse through relay R2and operates the other relays `as above described, but relay R does notoperate because the duration of the impulse is less than that necessaryto discharge the con- Vdenser C2 and in fact is only a very smallfraction of a second. At its first break contact Ra opens theshort-circuit across the relay R4fwhich energises over the circuit whichhas already been prepared at contact R30, Relay R4 closes its contactR4a to shunt relay R3 which releases and moves its contact Rflb to itsright hand position toprepare the circuit of the relay R5. It will benoted that once relay R4 has accepted the preparedc-ircuit, it is freeof the shunt effect of either vcontact-Rider contact REZ). Relay R5 nowreceives the impulses ofthe oscillations of Il5 volts which energisesrelay, RI whichestops its contacts Ria and Rib from oscillating. .Con-

tact' Rib thus remains closed but the motor. circuit is,` kept open at.contact Ra. Relay R4v remains locked untilCLdischarges, whereupon. relayR24 releasestobreak .thecomrnon return of relays'RB, R4,R5 at itscontact R2a. Contact 'RZb also opens and the relay, R4 releases toopenits contact Rfid `and allow its contact Ril-b to move to its left handposition. Welding can thus continuefat the readjusted arc current value.

" To raise the current a fleeting dead short isproduced which completesthe circuitspreviously described through relays R2 and R3. andY preparesthe circuit for the relay R4. Due to the Ishort duration of the deadshort relay. R6 cannot operate and the succeeding ee'ting `open-"circuit causes relay R4 to energise .as previously explained .toprepare the circuit forv relay. R5. Although contact R'la ilicks openupon thisopencircuit, it immediately closes again as soon asthefollowing dead short of 11/2 secondsfduration ,is started so that Cldoes not have time. to dis- LtactR-a to break the circuit of relayiRBwhich after a timedelay of 11/2 seconds, when condenser.C2 hasdischarged, releases and closes its con- "tact Rta in the motor circuitand itscontact R61) in thelocking circuit.

Upon restriking the arc contact Rla oscillates `but relays R2 and R5remain `held by the locking .circuit over contact R613. Relay R4 alsoremains energized. Upon drawing. the arc relay Rl is energizeclv andcontact Ria remains open, but relays R2 and-R5l remain held over contactR612. Contact'RIb closes the motor circuit through conktacts R3a and R3bin their left hand positions to drive the vmotor in a clockwisedirection to increase the current, the Aincreasing current `beingobservable in the arc.

The motor is 'stopped by open-circuting'the-arc 5 to 9 of`theaccompanying drawinglnallthese A.for a f' period :of one s secondeor longer when .the V.circuit operations previously .explainedtakeplace,

except that itis the relay R5 which closes its contact R5a tofcompletethe ,circuit of. therelay R6 whichfstopsthe motor. by opening `itscontact Ra.- andopens the.- locking circuit of relays R2 kand R5 at itscontact R612. lThe arc is then restruck and drawn aspreviouslyexplained, and welding continues at .thenewvalue'of the yarc current.

Tapping the electrode holder .on the wworkhas thesame effect as.restriking the-arc after an open-circuit to stop the motor, so` thatv ithas, no eiect on the currentfadjustment.. Ifthe operator should.faillto. restrike thearc .after preparngthe motor circuitlforaeitherraising or reducingthe current, the.fvwhole..cirouiteisrestoredtonormal,

. regardless .of which motor. circuit .,was, prepared,

since, as soonas the. arcI is .openfcircuited relay RT energizesandbreaksthe circuitpf relay R2 at its contact R'la which,.after.Cl .hasdischarged, releases to break thecOmmQn return circuitof relays'` R3, R4and R5at. its contactRZa.

Various simplified circuit arrangementsof Figs. 3 and liwill be.describedwith reference toFigs.

arrangements the current is `adjusted-.in .the downwards direction byproducinga deadshort by pressing the `electrode or theV electrode holderon to rthe work andl maintaining the dead short for a predeterminedminimum time,and. inthe upwards direction by a fleeting .dead shortfollowed by a longer dead short.of the.predeter Ymined time duration.

"Referring to thecircuit shownin Eig.. 5,.,1he

.apparatus comprisesj've. relays Rl. togR5 which are` suffixed to.indicatahe .numberofgrelax GQ11- vtacts controlled: by each relay.".jRe1ay.`..;RI,.-is

shunted across the arc circuit .andthe remaining four relays areoperatedY from aseparate 20-volt supply. RelayRZ is shunted byY arcondenserCl Yso as to give a time delay release operation of which openthe motor circuit in the maximum and minimum positions of the outputcurrent controller.

The circuit shows the relays in theirv conditions during normal welding.The mode of .operation of the circuit-isas follows. It will be assumedthat the operator is welding and desires to reduce the current outputfrom the generatoror other current supply means. To dothis he makes adead short by pressing the electrode, or'the electrode holder, on tothework which defenergizes the relay RI. At its contact Rlaa circuit iscompleted from the 20-volt; supply source to the relays R2'and R3 andthe circuit to the relay R5 is broken. Relay R2 energizes and at itscontact R2a completes the common return of relays R3 and R4. Relay R3energizes and at its contact R30 prepares the circuit of relay R4through the relay R3 and the contact R2a, `but Yrelay R4 cannot operatebecause it is shunted by contact Rla in its left-hand position.Relay'R3'- also shifts its contacts`R3a and R3b to their righthandposition to prepare the circuit of the motor for anti-clockwise rotationto move the output current controller in a direction to reduce thecurrent output.

After a time delay of 11/2 seconds lthe condenser C2v discharges and-releases relay R5 to complete -"13 the motor circuit' at its contactR5a, whereupon the motor starts and the arc current is reduced.

The operator holds the short circuit until he considers the current hasreached the desired new value and stopslthe motor by open-circuiting thearc. This energzes relay RI which moves its contact RI a to itsright-hand position and breaks the circuit for the relays R2 and R3 andmakes the circuit for the relay R which energizes to open its contactR5a to stop the motor. Since contact Rla no longer shunts relay R4, thisrelay is energised through therelay R3. At its contact R4b it breaks thecircuit of the relay R3 to prevent a dead short across condenser CI andcontact R4a closes immediately afterwards to complete a locking circuitfor the relay R4. Contact R4a .also shunts relay R3 which thereforereleases and allows its contacts R3a and R317 to return to their lefthand positions. After a period of one second the condenser Cl dischargesand releases relay R2 which breaks the common return at its contact R2ato open the circuit of relay R4 which thus cie-energizes. Restroking thearc produces fleeting dead shorts, the rst of which energises relay R3which is immediately tripped by relay R4 on the second impulse as abovedescribed. The fleeting impulses cause contact Ra to oscillate'lbutrelay R5 is held by the condenser C2 and the motor is thus not started.Upon drawing out the arc to its normal length the arc voltage againenergises relay Rl and the oscillation of contact Ria ceases and itremains in its right hand position to break the circuit of the relays R2and R3 and to complete the circuit of the relay R5. Relay R4 isde-energised due to the opening of contact Rza.

To increase the current a fleeting dead short is produced followed by afleeting open circuit and then a continuous dead short. The fleetingdead short de-energises relay RI which operates relays R2 and R3 andprepares the circuit for relay R4 as previously explained. On openingthe dead short the relay Rl again energises and breaks the circuit ofthe relays R2 and R3 to allow its contacts R3a and R3b to return totheir left-hand position and also energising relay R4. Relay R4 remainsenergised during this fleeting open circuit since relay R2 is held byits condenser CI and keeps its contact R2a closed, and upon the seconddead short being produced relay Rl again releases and at its contact Rabreaks the circuit of the relay R5. Relay R4 still remains energisedwith relay R3 de-energised, so

that after the condenser C2 has discharged relay R5 releases to completethe motor circuit at its contact R5a. The motor thus starts to move in aclockwise direction to drive the current controller in a direction toincrease the current, the operator holding the dead short until heconsiders that the current has reached the required new value.

The motor is then stopped by open-circuiting the arc to energise therelay Rl which moves its contact Rla to its right-hand position toenergise relay R5 which breaks the motor circuit at its contact R5a.After a delay of one second condenser Cl discharges and relay R2releases to break the common return at its contact Rla. Relay R4 thusdeenergises and releases its contacts to make the circuit ready for thenext controlling impulse or impulses. The arc is then restruck as abovedescribed and the welding proceeds with the current held at its newsetting.

Fig. 6 shows a modified circuit employing only "14 four relays. Toreduce the current one dead short is made as previously. Thisdeenergises relay RI which at its Contact Rla breaks the circuit ofrelay R4 and makes the circuit of relay R2. Relay R3, beingshort-circuited by its contact R3?) and the left contact of R2c, is notenergised. Relay R2 energises and changes its contacts R2a and R2b totheir right-hand positions for anti-clockwise rotation of the motor. Atthe contact R2c, it prepares the circuit for relay R3 'by moving to itsright-hand position. Relay R3,

being then short-circuited by contact Rla in its left-hand position inaddition to contact R327, still remains deenergised. After two secondscondenser C2 discharges through relay R4 and relay R4 releases and atits contact R4a completes the motor circuit to give the output currentcontroller in a direction to reduce the current.

The motor is stopped by open-circuiting the arc which energises relayRI. Its contact Rla breaks the circuit of relay R2 and makes the circuitof relay R4 which latter relay energises and breaks the motor circuit atits contact R4a to stop the motor. Although the circuit of relay R2 isbroken at contact Ria, R2 holds through the coil of relay R3 and contactR20 Iin its righthand position. Since both contacts Ra and R20 are intheir right-hand positions there is no shortcircuit across relay R3which therefore energises through the contact R2c in its right-handposition and the coil -of relay R2 so that for a fraction of a secondboth relay R2 and R3 are in series and energised. During this briefinterval condenser CI is charged. Relay R3 closes its contact R3a toprovide a locking circuit for itself which automatically short-circuitsrelay R2 which deenergises. It also opens its contact R3b. Upon therelease of relay R2, its contacts R2a and R227 return to their left-handpositions and its contact R20 moves to its left-hand position to breakthe circuit of relay R3. After one second condenser CI discharges andrelay R3 deenergises to release its contacts R3a and R31).

To increase the current two dead shorts are produced as previously. Therst dead short energises the relay R2 and prepares the circuit for relayR3 as previously. The fleeting open circuit arrives before condenser C2has time to discharge so that upon relay Rl energising again it breaksthe circuit of relay R2 at its Contact Rla and closes the circuit ofrelay R4, thus recharging condenser C2 before it has time fully todischarge. Relay R3 energises as above described and deenergises relayR2 which allows its contacts R2a and R2b to return to their left-handpositions. Before condenser Cl has time to discharge, however, thesecond dead short is produced and relay Rl is again released and allowsits contact Rla to return to its left-hand position to complete thecircuit to the relay R3 which rei mains energised. Since contact R317 isheld open, this second impulse from contact Ria cannot energise relay R2which; therefore, remains deenergised with its contacts R2a and R21) intheir left-hand positions. After a delay of two seconds condenser C2discharges and relay R4 releases to complete the motor circuit at itscontact R4a which then operates to drive the motor in a direction toincrease the current output.

The motor is again stopped by open-circuiting whereupon relay RIenergises and allows it contact Ria to return to its right-hand positiontherebi7 energising relay R4 which breaks the motor circuit at itscontact R4a. In moving to the right the contact Ria breaks the circuitof .15 relay Rtwhich .after condenser CI-discharges releases.

Upon striking the arc a series of fleeting dead shorts is produced, therst of which energises relay R2 and .the second energises relay R3 asabove described. During succeeding fleeting impulses contact Riaoscillates rapidly and also maintains the charge on the condensers CIand C2. Thus, although the motor circuit is prepared for clock-wiserunning it cannot start becauserelay R2 is held energised. Upon drawingout the arc to its normal length, contact Rla ceases to oscillate and isheld in its right-hand position. Relay R3 thus releases after its con-ldenser Cl yhas discharged and the circuit returns .to normal.

Fig. l shows a slight modification of a control arrangement employingfour relays in which the relays R2 and R3 are arranged in parallelinstead of in series as in the arrangement shown in Fig. 6.

With the arrangement shown'in Fig. 7 to reduce the current one deadshort is produced which releases relay RI. Its contact Ria moves to itsVleft-hand position and relay R2 is energised through contact RSa andthe normally closed lower contact of R2d. Relay R2 energises and closesits upper contact of R2d, which `moves its 'middle spring to open itslower contact. Relay R2 thus locks itself through its upper contact ofR262 and contact R3b. Its contact R20 moves to its right-hand positionto prepare the circuit for relay R3. Although relay R3 is now shuntedacross relay R4 and condenser C2, it will not energise from thedischarging current of the condenser C2 because it is of lowerresistance than relay R4. This arrangement necessitates, however, alarger capacity for the condenser C2 because when relay R3 is shuntedacross it by contact R moving to its right-hand position, the resistanceacross condenser C2 is reduced which increases the rate of discharge andwould, withoutsuch an increase in capacity, reduce the time Vdelay ofrelay R4.

Relay R2 also changes its contacts R2a and B2b to their right-handpositions to prepare the motor 'for anticlockwise rotation, and afterthe two seconds delay condenser C2 discharges and relay R4 de-energisesand releases its contact R4a to completefthe motor circuit.

The motor is stopped by open-circuiting the arc, whereupon relay RIenergises and moves its contact Rlc to its right-hand position tocomplete the circuit for relay R4, which opens its contact R4a to stopthe motor. Relay R3 becomes energised and at its contact R3a preparesanother circuit for itself. It opens its contact R31) to break thelocking circuit for relay R2 which releases and allows its contacts R2a,R2b and R2c to return to their left-hand positions. Relay R3 is Vheldenergised by the charge in condenser CI. The upper contact of R2d opensand allows its lower contact to close, but the circuit to the lefthandcontact of Ra 'is broken at R3a. After one lsecond condenser Cldischarges and relay R3 Vreleases to return the circuit to normal.Contact R311. returns to its left-hand position and contact R3?) closes.

To increase the current, the first dead short completes the circuits torelay R2 above described. The fleeting open circuit before condenser C2has time to discharge energises relay RI and -causes its contact Ria toreturn to its right-hand position. The Acircuit to relay R3 is thus com-.pleted as above described and rrelay R2 is deenergised. The second deadshortt-befoe condenser CI has had time to discharge causes-contactRia toreturn to. its left-hand position and completes the circuit to relay'RSthrough contact R3a, which is now in its right-hand position, andcontactiRllc, which is in its left-hand position. Since contact B3n. isi-n its right-hand position this second .impulse from contact Ria cannotreachrelay R2 which, therefore, remains deenergised. and its contactsRza and R219 remain in their left-hand-positions. After atime intervaloftwo seconds condenser C2 discharges and relay R4 deenel'gises tocomplete the motor circuit for clockwise rotation at its contact R4a.

The motor is stopped by open-circuiting the arc which energises relay Rland causes itscontact Ria to moveto its right-hand position to break thecircuit to relay R3 and make the circuit to relay R4 which latter breaksthe motor circuit at its contact R4a. After condenser C i dischargesrelay R3 releases and the circuit returns to normal.

Upon striking the arc a series of fleeting dead shorts is produced, therst and second lpreparing the circuits as shown for increasing thecurrent. The third and any succeeding short-circuits cause contact Riato oscillate whichA merely maintains condensers CI and C2 charged andprevents the motor circuit from being completed. Upon drawing the arc toits normallength contact Rla ceases to oscillate and is held vin itsright-hand position. Relay R3, thereforedeen ergises when the condenserCl discharges.

In the further mod'ication shown in Fig. `8 only three relays yare-usedin conjunction with .a separate 20-volt supply. The mode of operation ofthe circuit is as follows. To reduce the current a dead short isproduced which .releasesrelay R l. Its contact Ria moves to itsright-hand position thus breaking the circuit to relay Rl. Its contactRib moves to its left-hand position to break the circuit of relay R3 andpreparing the circuit for relay R2. After a time delay of two seconds,condenser C2 discharges and relay R3 releases and at its contact R311completes the motor circuit through contacts R2a and R2b vin theirleft-hand position to drive the motor in the direction to reduce thecurrent.

The motor is stopped by open-circuiting the arc. Upon open-circuitingthe voltage across the arc circuit rises to 40 volts or more and relaylR2 energises. Its contact R2c moves to its righthand position andtransfers relay R2 tothe separate 20-volt power supply via contact Ribinits left-hand position. Condenser CI charges and relay R2 changes itscontacts RZa and lR213 to their right-hand positions, Contact R2d alsocloses to remake the circuit to relay Rl which energises and moves itscontact Ria to itslefthand position to lock relay RI. Its contact Ribmoves to its right-hand position to break the circuit to relay R2. RelayR3 makes andat its contact R3a breaks the motor circuit. 'After a timeinterval of one second condenser Cl discharges and relay R2 releaseswhichallows its contacts to return to their normal positions, relay R'Ibeing held over contact Ria in its left-hand position.

To increase the current two dead shorts are produced, the first opensthe circuit to relay R3 as above described, but before R3 cande-energise due to the discharge of condenser C2 the fleeting opencircuit has restored contact Rlb toits righthand position and relay R2has energised and shifted its contacts R2a vand R213 to their rightfl?'hand positions as above described. The second .dead short againreleases Ri but this time relay R2 is energised having been held bycondenser Ci during the ileeting open circuit when contact ARib ickedover to its right-hand position. After a -delay of two seconds condenserC2 discharges and relay R3 releases to close its contact R3a to completethe motor circuit via contacts R2a and R2b .in their right-handpositions for driving the motor to increase the current.

'I'he motor is again stopped by open-circuiting the arc which energisesrelay Ri through contact ARZd, relay Ri locking itself by moving itscontact .Ria to its left-hand position. Contact Rib is moved to theright and completes the circuit for relay R3 which opens its contact R3ato stop the l.motor and after a delay of one second condenser Cidischarges to release relay R2 to return the 4circuit to normal. v

Upon striking the arc a series of dead shorts eis produced whichoscillate the contacts o'frelay RI to impart impulses to relay R3 andcondenser AC2 over contact Rib in its right-hand position. CThe .timeinterval between the pulses is so short l`that condenser C2 does notdischarge and relay '-R3, therefore, remains energised and-holdsthemotor circuit open. Upon drawing the arc toits normal length the arcvoltage stabilises at about y1'1 volts or more and Ri ceases tooscillate and remains energised.

A still further feature of the invention* as will be described withreference to Fig. 9 consists in connecting an electrically operatedclutch-in the Vdrive between the motor and the output vcurrentlcontroller whereby, when the motor is not operating, it is disconnectedfrom the spindle` of the :output current controller so that the lattermay be manually adjusted without moving the motor. I'This may beeffected, for example, by providing a solenoid which is connected inparallel or in series with the motor circuit so that when the latter isclosed the solenoid is actuated to cause a gear wheel to mesh in thegear train between the motor and the spindle of the output currentconvrtroller. The gear wheel automatically moves out of mesh, forexample under spring pressure, when the solenoid is de-energisd. The`solenoid may have a small piece of iron disposed-f' therein in order toincrease the magnetic ux and its power of attraction. l 1 .i A stillfurther feature of the invention which v,may be, applied to" any ofthea-arrangement described herein or in my above mentioned copendingapplication consists, as will be more 'fully described with reference toFig. 9, in the provision of a resistance in series with the controlcircuit shunted across the arc, the resistance being adjustable fordifferent cable lengths so that the voltage across the control circuitcan be adjusted to produce the correct operating voltages under allconditions. This resistance may b calibrated in cable lengths, beingincreased in value as the length of cable between the welding point andthe control unit increases. Instead of employing an adjustableresistance, a voltage regulating, arrangement, consisting for example ofa material as known under the registered trade-mark MetrosiL may be usedfor compensating for different cable lengths.

Fig. 9 shows a modification of the circuit arrangement illustrated inFig. 8. An additional relay R is provided which is the only relayshunted across the arc circuit. The relay R0 has only one contact Rlia,which is an advanl(RII energises and closes its contact Rila.

fl8 tage as this relay has to operate at rather critical voltages. Thecontrol circuit comprises the relays Ri, R2 and R3 which are fed fromthe 30 volt D. C. supply derived from the transformer T and rectifier Z.The diagram also shows the solenoid S connected in series with thecircuit of themotor M, which solenoid pulls the pinion P into engagementwith the gear wheel G on the shaft of theoutput current controller whenthe motor is operating and disengage the shaft of the current controllerwhen the motor is not running, thus enabling the current controller tobe manually adjusted without moving the motor.

:The motor is geared to the shaft carrying the pinion P through a geartrain.

In the circuit shown the motor M is an A. C. shaded pole motor whichonly requires one (changeover contact for reversing.

The diagram also shows the line compensating resistance L connected inseries with the relay 'R0 for the lpurpose of compensating for differentlengths of cable to the welding point.

The mode of operation of the circuit is as follows. To reduce thecurrent a dead short is produced which releases relay R0. Its contact Raopens and breaks the circuit of relay Ri.

Its contact Ria moves to its right-hand posi- `tion thus breaking thelocking circuit of relay Ri, and its contact Rib moves to its left-handposition to break the circuit of relay R3 and pre- .pare the circuit forrelay R2. After a time delay oi two seconds, condenser C2 discharges andrelay R3 releases and at its contact R3a completes the motor circuitthrough contact R2a in its left- `hand position to drive the motor inthe direction .to reduce the current, and simultaneously ener- -gisingthe solenoid S to cause the lpinion P to vengage with the gear wheelmounted on the shaft .of the output current controller.

The motor isl stopped by open-circuiting the arc. Upon open-circuitingthe voltage across the arc circuit rises to 40 volts or more and relayThis now completes the circuit of relay R2 via the left-hand contact ofR217, right-hand contact of Ria and Ra to the rectifier positive. RelayR2 ,energises and its contact R2b moves to its `right-hand position andtransfers R2 to the rectifier viaRib Vleft-hand contact. Condenser Cicharges and relay R2 changes its contact R2a to the right-hand position.Its other contact .R20 also closes to remake the circuit to relay Riwhich energises and moves its contact Ria to the left-hand position tolock relay Ri. Its contact Rib moves to its right-hand position to breakthe circuit of relay R2 and make the circuit of relay R3, which at itscontact R3a breaks the motor circuit and de-energises the solenoid S.After a time interval of one second condenser Ci discharges and relay R2releases which allows its contacts to return to their normal positions,i. e. R2a opens and R2a and R2b return to their left-hand positions.Relay Ri is held over its contact Ria in its left-hand position.

To increase the current two dead shorts are produced, the iirst opensthe circuit of relay R3 as l Rl, which again releases, but thstimerelay-'R2 is energisedhaving been held `by condenser vCl during thefleeting open circuit whenfcontact Rlb flicked over to its right-handposition.` After a delay of two Vseconds condenserCZ discharges andrelay R3 releases to closeits contact R3a to complete the motor andsolenoid circuit via contact R2a in its right-hand position for drivingthe motor to increase the current.

The motor is again stopped by open-circuiting the arc which energisesrelay R0 and its contact Ra closes to remake the circuitof relay Rl viathe closed contact R2c. Relay RI thus energises and locks itself bymoving its contactRI to its left-hand position. Contact Rlb moves to theright and completesl the circuit for relay R3 which opens its contactR3a to stop the motor and de-energise thesolenoid, andafter a delay ofone secondcondenser Cl discharges'to release relay R2 to return thecircuit to normal.

Upon striking the arc a series of dead shorts. is produced whichoscillate the contact ROLL-of relay R0. This in turn causes the contactsof relay RI to oscillate and impart impulses to relay R3 and condenserC2 each time its contact Rib flicks over to its right-hand position. Thetime interval between the impulses isso short that condenser C2V doesnot discharge and relay R3, therefore, remains energised and holds themotor circuit open. Upon drawing the arc to its normal length, thearcyoltage stabilises at about 17 volts or more with the result thatrelays R0 and Rl cease to oscillate and remain held in the energisedposition.

Although particular embodiments of theinmeans for said control circuit,a switch contact in said control circuit actuated by said voltageselective relay, means for causingV the rst time 453 'I The followingreferences are of record in the AIfile' of this patent: A

the L motor fis operating.

delay relay to'actate ein response toithewnumber or times. thesaidswitch. contact is. actuated, reversing. contacts in' the: motorcontrol circuit actuated@ byl said l first time'Y delay relay, meansresponsive tothe' first actuation'of saidvswitch contactl forienergisingthel secondV time delay relay, means 4for allowing said secondtime `delay relay'to fall oi afterv said switch contactl has remainedclosed lfor' a predetermined minimum time, and a starting contactconnected insaid motor control circuitactuated by said second timedelay: relay.

2.A Arrangement-for the remote control of the current supply inelectric;arc welding systems, comprising an-output currentcontroller forcontrolling the currentvsupplyqtothe,arc circuit, a reversible Velectricmotor for.A driving said output current controller, a voltageA selectiverelay shunted across the arc circuit, van adjustable re.- sistance.connected in series withsaid voltage selective relay, a control circuitcomprising two time delay relays, ,power supply meansrfor said controlcircuit, a switch contact in saidA control circuitactuated by=saidvoltage selective relay, means for causing the first time relay relayvto actuatein response to the number of times the said switchrcontactv isactuated, reversing contacts in the motorA control circuit actuatedbysaidfrsttime delay relay, means responsive to ated` by saidsecond time.delay relay, an electri- --cally operated clutch in the; drive betweenthe motor andv the' output' current controller, and

-means for operatingthe clutch to couple the motor'to the output currentcontroller onlyvwhen FRANK RIMMINGTON;

REFERENCES4 CITED UNITED STATES PATENTS Number Name Date i 392,370Sellon & Mordey Nov. 6, 18'88 :435,332 Thllly' Allg. 26', 1890 2,221,588Kovalsky Nov. 12, 1940

